Grate insert



FIG. 1 is a perspective view of a grate insert for a cooking assembly;

FIG. 2 is a second perspective view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is front view thereof, the rear view being a mirror image thereof;

FIG. 5 is a right side view thereof, the left side being a mirror image thereof; and,

FIG. 6 is a bottom view thereof.

The details shown in broken lines form no part of the claimed design. 

The ornamental design for a grate insert, as shown and described. 